Type 1 diabetes mellitus and its associated complications are a major health problem in the US. The disease, which originates from a breakdown in T-cell tolerance, has a significant pre-diabetic stage, during which effected individuals are essentially asymptomatic. This provides a window of opportunity for therapeutic intervention. Our aim is to generate an immune-based therapy that will selectively target the pathogenic cells without causing a global disturbance of the immune system. Productive interactions between T-cells and their targets are typically characterized by the formation of an "immune synapse" containing combinations of both clonotypic and oligotypic receptor-ligand pairs. Our central hypothesis is that antigen-specific therapy will require reagents which can mimic these events. As part of normal homeostatic mechanisms, T-cells stimulated through their antigen receptors can undergo activation induced apoptosis. This preferentially occurs to the potentially diabetogenic Th1 population, and is believed to be defective in at least some diabetic individuals due to a failure to induce pro-apoptotic molecules to sufficient levels. We will create synthetic antigen-specific pro-apoptotic molecules predicted to restore this functional deficit in vivo. These novel reagents should induce apoptosis of the targeted (pathogenic) cells, but spare potentially protective ones, and may therefore lead to a change in the immune balance, and tolerance. We will test this hypothesis using established model systems. The project will involve three phases. 1. The creation of single chain peptide-MHC class II complexes and chimeras with Fas ligand by molecular cloning techniques. 2. In vitro analysis of the reagents using a panel of antigen-specific T-cell clones, and primary cells isolated from transgenic, pre-diabetic or newly diabetic NOD mice. 3. Analysis of the reagents in vivo following adoptive transfer of diabetogenic cells into NOD/SCI mouse models of diabetes. Ultimately we envisage that this novel strategy will form the basis for improved therapies for pre-diabetic or newly diabetic human subjects.